The overall objectives of this proposal are to elucidate the ultrastructural and biochemical properties of different regions of the plasma membrane of mammalian spermatozoa, to identify developmental modifications of the sperm membrane which occur during epididymal maturation and capacitation, and to relate these changes to fertilization events. Electron microscopic techniques are being employed to study the glycocalyx, intramembranous particles and peripheral proteins of different regions of the sperm plasma membrane and efforts are being focused to identify changes in each of these components during post-testicular maturation. Subfractions of the sperm plasma membrane derived from discrete regions of the sperm surface are being isolated by biochemical procedures and differences in the protein composition of the subfractions are being determined by specific extraction procedures and SDS polyacrylamide gel electrophoresis. Structural-chemical experiments on isolated membrane fractions are being performed to identify which protein components contribute to the specific structural differentiation revealed by electron microscopic analysis. Biochemical changes in the sperm plasma membrane during epididymal maturation are being assessed by several biochemical procedures including enzymatic radiolabelling techniques. Experiments are being performed to determine which changes are due to binding of epididymal plasma or seminal plasma components to the sperm surface and which are due to a modificaton of pre-existing components.